1. Field of the Invention
The present invention relates to a protecting layer of a plasma display panel, a method of preparing the protecting layer, and a plasma display panel including the protecting layer, and more particularly, to a protecting layer comprising a magnesium oxide-containing layer having a surface to which magnesium oxide-containing particles having a magnesium vacancy-impurity center (VIC) are attached, a method of preparing the protecting layer, and a plasma display panel (PDP) including the protecting layer. This protecting layer having magnesium oxide particles at its surface is hardly damaged by plasma ions and has excellent electron emission performance, and thus, a PDP including the protecting layer has high reliability.
2. Description of the Related Art
Plasma display panels (PDPs) are self-emission devices that can be easily manufactured in a large size, and have good display quality and rapid response time. PDPs can also be manufactured to be thin, and thus, like LCDs, are suitable for wall displays.
FIG. 1 is a vertical cross-sectional view of a pixel portion of a PDP. Referring to FIG. 1, sustain electrodes 15, each including a transparent electrode 15a and a bus electrode 15b made of a metal, are formed on an inner surface of a front substrate 14. A first dielectric layer 16 is formed on the sustain electrodes 15. When the first dielectric layer 16 is directly exposed to a discharge space, discharging properties can be degraded and lifetime can be reduced. Therefore, a protecting layer 17 is formed on the first dielectric layer 16.
Meanwhile, an address electrode 11 is formed on a second substrate 10, and the address electrode 11 is covered by a second dielectric layer 12. The first substrate 14 and the second substrate 10 face each other, and are separated from each other by a predetermined distance. Barrier ribs 19 are interposed between the first substrate 14 and the second substrate 10 to define a discharge cell. A phosphor layer 13 is formed in the discharge cell. A gaseous mixture which generates ultraviolet rays is filled in the discharge cell. The gaseous mixture can be a mixture of Ne and Xe, or a gaseous mixture of He, Ne, and Xe at a predetermined pressure, for example, 450 Torr, in which Xe generates vacuum ultraviolet (VUV) rays (Xe ion: 147 nm of atomic rays; and Xe2: 173 nm of molecular rays), Ne reduces and stabilizes a discharge initiation voltage, and He increases mobility of Xe and increases emission of the molecular rays of Xe of 173 nm.
Generally, a protective layer of a PDP performs the following three functions.
First, a protecting layer protects an electrode and a dielectric layer. Discharging occurs even when only an electrode or a dielectric layer and an electrode are used. When only an electrode is used, it may be difficult to control a discharge current. When only a dielectric layer and an electrode are used, damage to the dielectric layer by sputtering may occur. Thus, the dielectric layer must be coated with a protective layer resistant to plasma ions.
Second, a protecting layer reduces a discharge initiation voltage. A discharge initiation voltage is directly correlated with the coefficient of secondary electron emission from a material constituting the protective layer against plasma ions. As more secondary electrons are emitted from the protecting layer, the discharge initiation voltage is reduced. In this regard, it is preferable to form a protective layer using a material with a high secondary electron emission coefficient.
Finally, a protecting layer reduces a discharge delay time. The discharge delay time refers to time needed to initiate discharge after a voltage is applied. The discharge delay time is the sum of a formation delay time Tf and a statistic delay time Ts. The formation delay time Tf is a time interval between the time when a voltage is applied and the time when a discharge current is generated, and the statistical delay time Ts is a statistical distribution of the formation delay time. The shorter the discharge delay time Tf is, the faster addressing is performed for a single scan method. Further, a shorter discharge delay time Tf can reduce scan drive costs, increase the number of sub-fields, and improve brightness and image quality.
A conventional protecting layer for a PDP can be formed by depositing a mono-crystalline magnesium oxide or a polycrystalline magnesium oxide on a substrate (see KR 2005-0073531). However, a PDP having such a conventional protecting layer has a high operating voltage, high power consumption, and long discharge delay time, and thus the conventional protecting layer is unsuitable for a HD PDP using a single scan method. Therefore, there is a need to develop a protecting layer with improved characteristics.